The invention relates to a water-cooled condenser in which the titanium condenser tubes are rolled and/or welded into a tube plate at each end and in which the titanium tube plates are bolted to the condenser casing and the header casing by means of flanges, the condenser casing of sheet steel being provided with explosion-bonded titanium plating at the connection location to the tube plates, which explosion-bonded titanium plating is welded in a watertight manner to the tube plates on the steam space side.
Such condensers, which are located at the so-called cold end of heat engines and have, as their purpose, to provide a steam turbine, for example, with a larger pressure drop and heat drop by generating a maximum possible vacuum, are known. If, in these condensers, the headers are connected to the tube plates and the condenser shell by means of flanges, the following problems are prevalent:
the machining of the extraordinarily large flanges for today's large condensers requires great effort on site; PA1 the danger fundamentally exists that air can penetrate into the steam space of the condenser because of the large flanges; PA1 leaking flanges can only be sealed subsequently in a very makeshift manner and with difficulty.
Power station operators now demand an extremely high level of sealing against cooling water penetration into the condensers. The permissible leakage rates are scarcely measurable and this leads to the previously used technique of rolling in the tubes being supplemented by welding in the tubes. In addition, extremely corrosion-resistant titanium tubes are now being used.
In the case of the flange connection described above, the possibility now also exists of rolling and/or welding the titanium tubes into titanium tube plates. This is particularly obvious because it is practically only possible to weld titanium to titanium. Appropriate seals must be provided for the bolting of the titanium tube plate to the flanges of both the header casing and the condenser casing. The rubber layer of the protective coating, which is necessary in any case, is therefore located between header casing and tube plate while a soft seal is inserted between tube plate and flange of the condenser casing. After a fairly long operating period, such a solution can, however, lead to penetration of both cooling water and air into the steam space because the seals are very heavily loaded due to the different expansions between the tubes and the condenser shell.
A water-cooled condenser with a steel condenser casing is known from U.S. Pat. No. 4,252,182, in which condenser titanium tubes penetrate a steel tube plate and are rolled into it; their ends are welded into a special titanium plate placed in front of the tube plate. The problems of the otherwise conventional tube/tube plate welded connection are solved by this configuration. The titanium plate itself is directly bolted to the header and is bolted to the tube plate via distance elements. The tube plate is also bolted to the condenser casing. Because, with this arrangement, a steel tube plate is to be connected to a steel condenser casing, no material technology difficulties arise even if, in the case shown, air penetration into the steam space of the condenser must possibly be expected because of the use of bolting alone.
Also known from U.S. Pat. No. 4,562,887 is a flange connection, of the type described above, in which the end surface of the flange to be bolted to the tube plate is provided with explosion plating. After the fitting of the tube plates to the condenser casing, this explosion plating is welded to the tube plates. Although, in this solution, the explosion plating is subjected exclusively to compression and can therefore not separate from the flange, the weld seam could be damaged for some reason and in this case, the possibility exists of air penetration and, in particular, of cooling water penetration via leaking protective coatings and the bolt holes.
The object of the invention is therefore to create, in a condenser of the type described above, a connection which can be inspected between the titanium tube plate and the steel sheet of the flange/condenser casing.
In accordance with the invention this object is achieved in that explosion-bonded titanium plating is applied to the steam space side part of the flange and that the flange bolting arrangement is located outside the sealing surface between the flange and the tube plate.
In addition to the fact that the critical point in flange designs is now provided with an absolutely leaktight welded connection, the advantage of the invention may be particularly seen in that even in the case of a leaking weld seam between the explosion plating and the tube plate, the sealing surface is accessible from outside for repair purposes.